1. Field of the Invention
The present invention relates to engines that are operated by a pressurized fluid to provide a usable work output. More particularly, the present invention relates to an improved form of pressurized-fluid-operated engine in which a portion of the exhausted fluid is recycled and mixed with incoming pressurized fluid to provide greater efficiency.
2. Description of the Related Art
Engines in which power is derived from partially expanding a pressurized fluid to drive an output shaft are preferred over internal combustion engines because the latter generally involve the handling of volatile combustible fluids, such as gasoline, diesel fuel, and any of a number of combustible gases. Moreover, such internal combustion engines result in exhaust gases that are ecologically undesirable, because they could possibly cause air pollution and sometimes health risks, depending upon the combustion products that result from the combustion process and depending upon the completeness of combustion. Additionally, such internal combustion engines require complex fluid metering systems to meter the combustible fluid in the proper amounts for proper combustion, and because of the generation of significant heat, such engines usually require some type of engine-driven cooling system in order to avoid overheating of the engine components.
Engines utilizing pressurized gases, such as compressed air and natural gas provided under pressure, can be used to power an engine by virtue of the pressure of the gas, and without combustion, to overcome the disadvantages of the internal combustion process. Examples of such pressure-fluid operated engines are disclosed in the following U.S. Patents, each of which issued to John E. Holleyman, the inventor in the present application: U.S. Pat. No. 3,925,984, which issued Dec. 16, 1975, and is entitled: "Compressed Air Power Plant"; U.S. Pat. No. 4,162,614, which issued July 31, 1979, and is entitled: "Pressure Fluid Operated Power Plant"; and U.S. Pat. No. 4,507,918, which issued Apr. 2, 1985, and is entitled: "Reciprocating Piston Compressed Fluid Engine Having Radial Cylinders and Triggerable Valves."
Although the various engine constructions disclosed in the above-identified patents provide satisfactory results, it is desirable that the operating efficiency of such engines be further improved for greater commercial acceptability.
It is an object of the present invention to provide a pressure-fluid operated engine that has improved efficiency.